Traiettoria for piano and electronic sounds (1982-1988), by Marco Stroppa, is one of the key works of mixed genre in the period of the 1980s; it is to be considered on a par with Karlheinz Stockhausen’s famous mixed genre Kontakte of 1959. Traiettoria, however, is the work of a very young composer. In the early 1980s, at least at the beginning of the project, Stroppa’s style was by no means fixed. It was during the elaboration of his first important work that his compositional workshop was firmly established. The compositional procedures employed in Traiettoria then became the composer’s normal language. Following step-by-step the progress of the creation of the three movements which constitute his masterpiece, we can observe the evolution of his compositional techniques and processes: the learning phase (both musical and scientific) that was part and parcel of his first creative intuitions, and the final months of the composition, during which Stroppa became lucidly self-conscious of his compositional process. Furthermore, the analysis of the genetic construction of Traiettoria and of various educational and “self-reflexive” documents of Stroppa himself, including his academic transcripts, to which may be added observations on the transfer of compositional procedures into his most recent works (using contemporary software), would appear to be essential not only for the comprehension of the work itself, but also for the comprehension of the nature of the composer’s wider compositional laboratory.